Query asset property notifications in Amazon IoT SiteWise - Amazon IoT SiteWise
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Query asset property notifications in Amazon IoT SiteWise

To query asset property notifications, create Amazon IoT Core rules made up of SQL statements.

Amazon IoT SiteWise publishes asset property data updates to Amazon IoT Core in the following format.

{
  "type": "PropertyValueUpdate",
  "payload": {
    "assetId": "String",
    "propertyId": "String",
    "values": [
      {
        "timestamp": {
          "timeInSeconds": Number,
          "offsetInNanos": Number
        },
        "quality": "String",
        "value": {
          "booleanValue": Boolean,
          "doubleValue": Number,
          "integerValue": Number,
          "stringValue": "String"
        }
      }
    ]
  }
}

Each structure in the values list is a timestamp-quality-value (TQV) structure.

  • The timestamp contains the current Unix epoch time in seconds with nanosecond offset.

  • The quality contains one of the following strings that indicate the quality of the data point:

    • GOOD – The data isn't affected by any issues.

    • BAD – The data is affected by an issue such as sensor failure.

    • UNCERTAIN – The data is affected by an issue such as sensor inaccuracy.

  • The value contains one of the following fields, depending on the type of the property:

    • booleanValue

    • doubleValue

    • integerValue

    • stringValue

To parse values out of the values array, you need to use complex nested object queries in your rules' SQL statements. For more information, see Nested object queries in the Amazon IoT Developer Guide, or see the Publish property value updates to Amazon DynamoDB tutorial for a specific example of parsing asset property notification messages.

Example query to extract the array of values

The following statement demonstrates how to query the array of updated property values for a specific double-type property on all assets with that property.

SELECT
  (SELECT VALUE (value.doubleValue) FROM payload.values) AS windspeed
FROM
  '$aws/sitewise/asset-models/a1b2c3d4-5678-90ab-cdef-11111EXAMPLE/assets/+/properties/a1b2c3d4-5678-90ab-cdef-33333EXAMPLE' 
WHERE
  type = 'PropertyValueUpdate'

The previous rule query statement outputs data in the following format.

{
  "windspeed": [
    26.32020195042838,
    26.282584572975477,
    26.352566977372508,
    26.283084346171442,
    26.571883739599322,
    26.60684140743005,
    26.628738636715045,
    26.273486932802125,
    26.436379105473964,
    26.600590095377303
  ]
}
Example query to extract a single value

The following statement demonstrates how to query the first value from the array of property values for a specific double-type property on all assets with that property.

SELECT
  get((SELECT VALUE (value.doubleValue) FROM payload.values), 0) AS windspeed
FROM
  '$aws/sitewise/asset-models/a1b2c3d4-5678-90ab-cdef-11111EXAMPLE/assets/+/properties/a1b2c3d4-5678-90ab-cdef-33333EXAMPLE' 
WHERE
  type = 'PropertyValueUpdate'

The previous rule query statement outputs data in the following format.

{
  "windspeed": 26.32020195042838
}
Important

This rule query statement ignores value updates other than the first in each batch. Each batch can contain up to 10 values. If you need to include the remaining values, you must set up a more complex solution to output asset property values to other services. For example, you can set up a rule with an Amazon Lambda action to republish each value in the array to another topic, and set up another rule to query that topic and publish each value to the desired rule action.